Conventionally, there has been known an inlet pipe structure which is provided in a vehicle such as an automobile having a plurality of fuel tanks, and an example thereof is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 3-79431.
Further, there has also been proposed a technique in which a main tank 71 and a sub-tank 75 are each formed as a separate body in a state of being not connected by a communicating pipe and an inlet pipe 90 is branched into two pipes 90A, 90B, one inlet pipe 90A being connected to the main tank 71 and another inlet pipe 90B being connected to the subtank 75, in order to secure fuel during long-distance traveling (see FIG. 4). However, for example, when the sub-tank 75 is in a full-filled state, peripheral atmosphere heat and heat of returned fuel from an engine cause a fuel 81 within the sub-tank 75 to be heated and vapor (vaporized fuel) is generated, thereby resulting in an increase in the internal pressure of the sub-tank 75. Accordingly, in order to prevent a liquid surface of the fuel 81 in the sub-tank 75, flowing through a breather tube 94 connected to the sub-tank 75, from ascending to the vicinity of a fueling port 94, a liquid-level monitoring device 100 needs to be provided additionally. In FIG. 4, reference numerals 96, 98 each designate a check valve.
Techniques relating to the present invention are disclosed in the following publications: Japanese Patent Application Laid-Open (JP-A) No. 52-87574 in which a communicating pipe is provided between a main tank and a sub-tank; Japanese Utility Model Application Laid-Open (JP-U) No. 61-24318 in which an inlet pipe is disposed at a position above a fuel level even in an inclined state; Japanese Utility Model Application Laid-Open (JP-U) No. 2-42817 in which a baffle plate for preventing back flow of fuel is provided at a breather opening portion; Japanese Utility Model Application Laid-Open (JP-U) No. 3-17398 in which a metallic retainer of an inlet pipe is formed by press molding and the number of parts is thereby reduced; and the technical review published by Japan Patent Information Organization No. 87-14727 in which fueling-gun insertion openings are respectively provided for a main tank and a sub-tank.